Vinylic hindered amine light stabilizers

ABSTRACT

Vinylic hindered amine light stabilizers as novel polylmerizable light stabilizers are disclosed and have the general formula (I):wherein:R1 is C1 to C8: alkyl, alkoxy, alkyl phenyl, hydroxy alkyl (all linear and branched), allyl, acyl, cycloalkyl (cyclopentyl, cyclohexyl or curnyl: linear and branched); R2 is hydrogen and methyl, R3 is vinyl, C1-C4 vinyl alkyl [H2C=C(R4)C1-C4], R4 is H, C1-C4 alky and alkyl phenyl and R5 is H, C1-C4 alkyl, X is O, NH, C1-C8 alkyloxy and alkylamino: (linear or branched).

FIELD OF INVENTION

This invention relates to vinylic-derivatives of Hindered Amine Light Stabilizer (HALS) having general formula (I):

wherein:

R₁ is C₁ to C₈ alkyl, alkoxy, alkyl phenyl, hydroxy alkyl (all linear and branched), allyl, acyl, cycloalkyl (cyclopentyl, cyclohexyl or cumyl: linear and branched); R₂ is hydrogen and methyl, R₃ is vinyl, C₁-C₄ vinyl alkyl [H₂C═C(R₄)C₁-C₄] R₄ is H, C₁-C₄ alkyl and alkyl phenyl and R₅ is H, C₁-C₄ alkyl, X is O, NH, C₁-C₈ alkyloxy and alkylamino: (linear or branched) and the process for the synthesis thereof.

BACKGROUND OF INVENTION

Monomeric hindered amine light stabilizers are gaining much more importance to stabilize the polyolefins and dicne elastomers. Natural and synthetic polymers in common use are susceptible to photo-oxidative degradation upon exposure to natural and artificial weathering. The deterioration of these polymeric materials is mainly due to the UV portion of sunlight reaching the earth surface. The net result of degradation is the loss in the Molecular weight and macroscopic physical properties. Polyolefins and unsaturated synthetic elastomers, being highly sensitive to oxidation, require the addition of stabilizers to provide protection during processing, storage and end-use. The low Molecular weight stabilizers are easily lost from the polymer through evaporation, migration and extraction but, the compatible and mobile stabilizers usually give the best protection. In older to avoid this loss polymer-bound and polymeric stabilizes have been devised. Moreover, since the degradation of a polymer commences from the surface and slowly proceeds into the matrix of the polymeric substrate, the stabilizers are therefore expected to be most potent if they are concentrated at the surface. Therefore, they should be anchored covalently to the polymer surface. Monomeric light stabilizers thus prove to be the best choice to attain the desired photostability.

A discrete literature on the synthesis of the vinylic derivatives of HALS is available; some of these methods are quite trivial and employ complex routes using expensive reagents. Following patents and literature: DE 2950067 (January 1981); DE 2642446 (March 1978),; F. E. Karrer, Markromol. Chem. 181, 595 (German) 1980, N. S. Prostakov, A. V. Varlomov and G. A. Vasilev, Khim., Geterotsikl. Soedin., 6, 787 (Russian) 1977, JP 53015385 (February 1978); D. V. Sokolov, M. N. Akimova, K. D. Praliev, V. M. Kurilenko, Zh. N. Khlienko and K M. Moiseeva, Khim.-Farm. Zh. 11, 47 (Russian) 1977; P. Hrdlovic and S. Chmela, Int. J. Polym. Mater., 13, 245 (1990); J. Pan, Z. Yang, L. Tong, W. Lau, W. Y. Wayne and C. S. Lee, Polym. Degrad. Stab. 44, 85, 1994; disclose the preparation and the mechanism of application of HALS derivatives.

Some of the authors have reported vinylic derivatives of HALS as polymerizable light stabilizers wherein, the vinyl group is attached to the hindered nitrogen atom. One of the vinylic derivative of HALS having formula

is disclosed in the patent EP 24999145 A1 (December 1987). Upon UV irradiation under atmospheric condition; the hindered nitrogen bearing the vinyl group gets converted into nitroxyl radical (N—O*).

As a result of which the hindered amine moiety gets detached from the covalently bonded vinyl group attached to the surface and is thus prone to be lost due to leaching/extraction/evaporation (shown in the Scheme 1), making it inefficient. The objective of the present invention is therefore, to provide a process for the preparation of novel vinylic HALS, which can the firmly bound to the polymer surface. Moreover, this class of monomeric HALS are known to be compatible with polyolefins, polystyrene and diene clastomers and can even be co-polymerized in a desired proportion to obtain ‘in chain’ and ‘chain end’ radical scavengers.

DESCRIPTION OF THE INVENTION

Accordingly the present invention provides novel vinylic Hindered Amine Light Stabilizers derivatives having general formula (I):

R₁ is C₁ to C₈: alkyl, alkoxy, alkyl phenyl, hydroxy alkyl (all linear and branched), allyl, acyl, cycloalklyl (cyclopentyl, cyclohexyl or cumyl: linear and branched); R₂ is hydrogen and methyl, R₃ is vinyl, C₁-C₄ vinyl alkyl [H₂C═C(R₄)C₁-C₄], R₄ is H, C₁-C₄ allyl and alkyl phenyl and R₅ is H, C₁-C₄ alkyl, X is O, N C₁-C₈ alkyloxy and alkylamino: (linear or branched).

In one of the other embodiments of the present invention, the carbonyl compound having formula (III) used to react with compound having formula (II) is selected from formalin, formaldehyde, acetaldehyde, benzaldehyde, methyl ethyl ketone, methyl benzyl ketone, cyclohexyl methyl ketone.

In yet another embodiments of the present invention, the organic solvent used for extracting the products is selected from the group consisting of diethylether; dieliloromethane, ethyl acetate and benzene.

In another embodiment the catalyst use is selected from the group consisting of alkyl substituted amino pyridines exemplified by N,N-dimethyl-4-aminopyridine-(DMAP) 4-amino pyridine and 2-mercaptobenzoxazole.

In yet another embodiment the dry organic sloven used to dissolve the catalyst and compound (IV) is selected from the group consisting of dieliloromethane dichloroethane, carbon tetrachloride, cyclohexane, n-hexane and chlorobenzene.

In still another embodiment the base used is selected from aliphatic and aromatic substituted amine selected from the group consisting of triethyl amine, trimethyl amine 2,6-lutidine and pyridine.

In another embodiment the compound (V) added to react with compound (IV) is selected from the group consisting of acryloyl chloride, methacryloyl chloride, pentenoyl chloride and 3-butenoyl chloride-3-phenyl.

In yet another embodiment the inert gas used is selected from Nitrogen and Argon.

In yet another embodiment the inorganic base used to neutralize the solvent fraction containing the product is selected from the group consisting of sodium carbonate and pottassium sodium bicarbonate, potassium carbonate.

HALS monomers and some of its derivatives may be prepared by any of the methods known in the art including those disclosed in Patents No. JP 53015385 28 (July 1978), Swiss CH 610898 (May 15, 1979), Swiss CH 605927 (October 1978), Brit. GB 1492494 (November 1977) and Literature: T. Tsuchiya and H. Sashida, Heterocycles, 14, 1925-8 (1980). All these patents are incorporated herein by reference. HALS namely 2,2,6,6-tetramethyl piperidine and 2,2,6,6-tetramethyl-4-piperidinol may be prepared by synthetic route disclosed by W. B. Lutz, S. Lazams and R. I. Meltzer, J. Org. Chem., 14, 530 (1949). All these patents and literature are incorporated herein by reference The present invention is described herein below with references to examples which are illustrative only and should not be construed to limit the scope of the present invention in any manner whatsoever.

EXAMPLE 1 Synthesis of 1,2,2,6,6-pentamethy-4-piperidinol

1,2,2,6,6-pentamethyl-4-piperidinol was synthesized upon reductive-amination of 2,2,6,6-tetramethy-4-piperidinol. A mixture of 2,2,6,6-tetranmethyl-4-piperidinol (3.55 g, 0.02 M), 37% formalin (3.3 mL) and 1 mL formic acid was heated under a reflux condenser on the steam bath for 5 h. The reaction mixture was made basic with (1.0 M) potassium hydroxide solution and the product was extracted with ether (5×50 mL). The combined extract was washed with saturated solution of potassium carbonate (2×20 mL) and dried over anhydrous magnesium sulfate and finally the solvent was evaporated under vacuum. The residue was then sublimed at 0.05 mm, bath temperature 85° C. The white sublimate weighed 3.5 g to give 91% yield, mp=72-74° C.

EXAMPLE 2 Synthesis of 1,2,2,6,6-pentamethyl piperidinyl-4-acrylate

This model compound was synthesized strictly under dry and inert reaction conditions. 1,2,2,6,6-pentamethyl-4-piperidinol (1.0 g, 0.00588 M) was taken in a two necked 25 mL capacity round bottom flask (RB) along with 4-dimethyl aminopyridine (DMAP) (30 mg, 0.245 mM) and was kept under nitrogen atomsphere. Dry dichloromethane (15 mL) was injected into the tightly closed RB through the rubber septum, followed by dry triethyl amine (TEA) (1.2 mL, 0.0087 M). This reaction mixture was stirred for 10 minutes at room temperature followed by the addition of acryloyl chloride (0.55 mL, 0.0069 M) with stirring. The reaction mixture was agitated at room temperature for 10 hrs. This reaction mixture was then quenched in ice water, and the product was extracted in dichloromethane (4×25 mL). The combined extract was given (2×20 mL) washes of saturated sodium bicarbonate solution and finally dried over anhydrous magnesium sulfate. The solvent was evaporated under vacuum at 38° C. over a rotavapor. The product was found to be almost pure (97.8% by Gas Chromatography). The TLC didn't show any spot of either the starting material or the catalyst (DMAP). The 1,2,2,6,6-pentamethy piperidinyl-4-acrylate yield was 1.11 g (85%).

EXAMPLE 3 Synthesis of 1,2,2,6,6-pentamethyl piperidinyl-4-acrylamide

This compound was synthesized strictly under dry and inert reaction conditions. 1,2,2,6,6-pentamethy-4-aminopiperidine (1.0 g, 0.00584 M) was taken in a two necked 25 mL capacity RB along with 4-dimethyl aminopyridine (DMAP) (35 mg 0.28 mM and was kept under nitrogen atmosphere. Dry dichloromethane (15 mL) was injected into the tightly closed RB through the rubber septum, followed by dry triethyl amine (TEA) (1.2 mL, 0.0087M). This reaction mixture was stirred for 10 minutes at 10-12° C. followed by the gradual addition of acryloyl chloride (0.55 mL 0.0069 M) with stirring at 0-5° C. The reaction mixture then, was allowed to stir at room temperature for approximately 10 hrs. This reaction mixture was then quenched in ice water, and the product was extracted in dichloromethane (4×25 mL). The combined extract was given (2×20 mL) washes of saturated potassium bicarbonate solution and finally dried over anhydrous magnesium sulfate. The solvent was evaporated under vacuum at 38° C. over a rotavapor. The crude product was found to be 89.8% pure (by Gas Chromatography). It was further purified by column chromatography. The yield of 1,2,2,4,4-pentamethy piperidinyl-4-acrylamide after purification was found to be 1.15 g (88%).

EXAMPLE 4 Synthesis of 1-pentyl-2,2,6,6-tetramethyl piperidinyl-4-acrylate

1-tert-pentyl-2,2,6,6-tetramethy-4-piperidinol was synthesizd strictly under dry and inert reaction conditions. 1-tert-pentyl-2,2,6,6-tetramethy-4-piperidinol (2.0 g, 0.00876 M) was taken in a two necked 50 ml capacity round bottom flask (RB) along with 4-dimethyl aminopyridine (DMAP) (53.5 mg, 0.437 mM) and was kept under nitrogen atmosphere. Dry dichloromethane (25 mL) was injected into the tightly closed RB through the rubber septum, followed by dry triethyl amine (TEA) (1.83 mL, 0.0131 M). This reaction mixture was stirred for 10 minutes at room temperature followed by the addition of acryloyl chloride (0.85 mL, 0.0105 M) with stirring. The reaction mixture was agitated at room temperature for 10 hrs. This reaction mixture was then quenched in ice water, and the product was extracted in dichloromethane (4×25 mL). The combined extract was given (2×20 mL) washes of saturated potassium bicarbonate solution and finally dried over anhydrous magnesium sulfate. The solvent was evaporated under vacuum at 38° C. over a rotavapor and the product was found to be almost pure. The TLC didn't show any spot of either the starting material or the catalyst (DMAP). The yield of the product was 2.10 g (85%).

EXAMPLE 5 Synthesis of 1-allyl-2,2,6,6-tetramethyl piperidinyl-4-acrylate

1-allyl-2,2,6,6-tetramethy-4-piperidinol (1.5 g, 0.00756 M) was taken in a two necked 50 ml capacity round bottom flask (RB) along with 4-dimethyl aminopyridine (DMAP) (46.2 mg, 0.387 mM) and was kept under nitrogen atmosphere. Dry n-bexane (25 mL ) was injected into the tightly closed RB through the rubber septum, followed by dry triethyl amine (TEA) (1.73 mL, 0.0124 M). This reaction mixture was stirred for 10 minutes at 10° C. followed by the addition of acryloyl chloride (0.79 mL, 0.0098 M) with stirring at 0° C. The reaction mixture was agitated initially for 3 hrs at 5° C. and for the remaining period at room temperature for approximately 9 hrs under nitrogen atmosphere. This reaction mixture was then quenched in ice water, and the product was extracted in n-hexane (4×25 mL). The combined extract was given (2×20 mL) washes of saturated potassium bicarbonate solution and finally dried over anhydrous magnesium sulfate. The solvent was evaporated under vacuum at 38° C. over a rotavapor. The crude yield of 1-allyl-2,2,6,6-tetramethy piperidinyl-4-acrylate was 1.65 g (86.5%).

EXAMPLE 6 Synthesis of 1-methyleylcohexyl-2,2,6,6-tetramethyl piperidinyl-4-acrylate

This desired compound was synthesized strictly under dry and inert reaction conditions. 1-methyleylcohexyl-2,2,6,6-tetramethyl piperidinol (1.0 g, 0.00588 M) was taken in a two necked 25 ml capacity round bottom flask (RB) along with 4-dimethyl aminopyridine (DMAP) (30 mg, 0.245 mM) and was kept under nitrogen atomsphere. Dry dichloromethane (15 mL) was injected into the tightly closed RB through the rubber septum, followed by dry triethyl amine (TEA) (1.2 mL, 0.0087 M). This reaction mixture was stirred for 10 minutes at room temperature followed by the addition of acryloyl chloride (0.55 mL, 0.0069 M) with stirring at 5° C. The reaction mixture was agitated at room temperature for 10 hrs. This reaction mixture was then quenched in ice water, and the product was extracted in dichloromethane (4×25 mL). The combined extract was given (2×20 mL) washes of saturated potassium bicarbonate solution and finally dried over anhydrous magnesium sulfate. The solvent was evaporated under vacuum at 38° C. over a rotavapor. The product was found to be almost pure (97.8% by Gas Chromatography). The TLC didn't show any spot of either the starting material or the catalyst (DMAP). The yield of 1-methyleylcohexyl-2,2,6,6-tetramethyl piperidinyl-4-acrylate was found to be 1.003 g (82.89%).

EXAMPLE 7 Synthesls of 1-ethylphenyl-2,2,6,6-tetramethyl piperidinyl-4-acrylate

1-ethylphenyl-2,2,6,6-tetramethyl-4-piperidinol (2.0 g, 0.0076 M) was taken in a two necked 50 mL capacity round bottom flask (RB) along with 4-dimethyl aminopyridine (DMAP) (46.5 mg, 0.387 mM) and was kept under nitrogen atomsphere. Dry carbon tetrachloride (25 mL) was injected into the tightly closed RB through the rubber septum, followed by dry pyridine (0.907 mL, 0.0112 M). This reaction mixture was stirred for 10 minutes at 10-12° C. followed by the addition of acryloyl chloride (0.75 mL, 0.0098 M) with stirring at 5° C. The reaction mixture was agitated at room temperature for approximately 13 hrs. This reaction mixture was then quenched in ice water, and the product was extracted in ethylacetate (4×25 mL). The combined extract was given (2×20 mL) washes of saturated potassium bicarbonate solution and finally dried over anhydrous magnesium sulfate. The solvent was evaporated under vacuum at 38° C. The yield of 1-ethylphenyl-2,2,6,6-tetramethyl piperidinyl-4-acrylate was 1.93 g (80%).

EXAMPLE 8 Synthesis of 1-methyl-2,6-diethyl-2,6-dimehylpiperidinyl-4-acrylate

1-methyl-2,6-diethyl-2,6-dimethyl-4-piperidinol (2.5 g, 0.0125 M was taken in a two necked 50 mL capacity round bottom flask (RB) along with 4-dimethyl aminopyridine (DMAP) (76.5 mg, 0.625 mM) and was kept under nitrogen atomsphere. Dry dichloroethane (35 mL) was injected into the tightly closed RB through the rubber septum, followed by dry triethyl amine (TEA) (2.6 ML, 0.0187 M). This reaction mixture was stirred for 10 minutes at room temperature followed by the addition of acryloyl chloride (0.75 mL, 0.0098 M) with stirring at 5° C. The reaction mixture was agitated at room temperature for 10 hrs. This reaction mixture was then quenched in ice water, and the product was extracted in dichloromethane (4×25 mL). The combined extract was given (2×20 mL) washes of saturated potassium bicarbonate solution and finally dried over anhydrous magnesium sulfate. The solvent was evaporated under vacuum at 38° C. The 1-methyl-2,6-diethyl-2,6-dimethyl piperidinyl-4-acrylate was found to be almost pure and its yield was 2.85 g (90%).

EXAMPLE 9 Synthesis 1-methyl-2,6-diethyl-2,6-dimehylpiperidinyl-4-acrylamide

1-methyl-2,6-diethyl-2,6-dimethyl-4-aminopiperidine (2.0 g, 0.010 M) was taken in a two necked 50 mL capacity round bottom flask (RB) along with 4-dimethyl aminopyridine (DMAP) (61.5 mg, 0.5 mM) and was kept under nitrogen atmosphere. Dry chlorobenzene (35 mL) was injected into the tightly closed RB through the rubber septum, followed by dry triethyl amine (TEA) (1.96 mL, 0.0141 M). This reaction mixture was stirred for 10 minutes at 15° C. followed by gradual addition of acryloyl chloride (0.75 mL, 0.0098 M) with stirring at 0-5° C. The reaction mixture was initially agitated at 5° C. for 3 hrs followed by stirring at room temperature for 10 hrs. This reaction mixture was then quenched in ice water, and the product was extracted in diethylether (4×25 mL). The combined extract was given (2×20 mL) washes of saturated potassium bicarbonate solution and finally dried over anhydrous magnesium sulfate. The solvent was evaporated under vacuum at 38° C. over a rotavapor. The product was found to be 85% pure and was further purified by column chromatography under nitrogen atmosphere. The yield of the reaction was 2.03 g (81%).

EXAMPLE 10 Synthesis of 1,2,2,4,6,6-hexamethyl piperidinyl-4-acrylate

1,2,2,4,6,6-hexamethyl piperidinol (1.5 g, 0.0081 M was taken in a two necked 50 mL capacity round bottom flask (RB) along with 4-dimethyl aminopyridine (DMAP) (49.5 mg, 0.405 mM) and was kept under nitrogen atomsphere. Dry dichloromethane (30 mL) was injected into the tightly closed RB through the rubber septum, followed by dry triethyl amine (TEA) (1.7 ml, 0.0121 M). This reaction mixture was stirred for 10 minutes at room temperature followed by the addition of acryloyl chloride (0.77 mL, 0.0097 M) with stirring at 5° C. The reaction mixture was agitated at room temperature for 10 hrs. This reaction mixture was then quenched in ice water, and the product was extracted in dichloromethane (4×25 mL). The combined extract was given (2×20 mL) washes of saturated potassium bicarbonate solution and finally dried over anhydrous magnesium sulfate. The solvent was evaporated under vacuum at 38° C. The product was found to be almost pure (98% pure by GC). 1,2,2,4,6,-hexamethyl piperidinyl-4-acrylate obtained at the end of the reaction was 1,77 g ((91.4%).

EXAMPLE 11 Synthesis of 1,2,2,4,6,6-hexamethyl peridinyl-4-acrylamide

1,2,2,4,6,6-hexamethyl-4-aminopiperidine (2.0 g, 0.0108 M) was taken in a two necked 50 mL capacity round bottom flask (RB) along with 4-dimethyl aminopyridine (DMAP) (66.5 mg, 0.543 mM) and was kept under nitrogen atomsphere. Dry dichloromethane (30 mL) was injected into the tightly closed RB through the rubber septum, followed by dry triethyl amine (TEA) (2.1 mL, 0.015 M). This reaction mixture was stirred for 10 minutes at 15° C. followed by the gradual addition of acryloyl chloride (0.86 mL, 0.01087 M) with stirring at 0-5° C. initially for 2 hrs. The reaction mixture was then agitated at room temperature for 9 hrs. This reaction mixture was then quenched in ice water, and the product was extracted in dichloromethane (4×25 mL). The combined extract was given (2×20 mL) washes potassium bicarbonate solution and finally dried over anhydrous magnesium sulfate. The solvent was evaporated at 38° C. under vacuum over rotavapor. The product was found to be almost pure (97.2% pure by GC). The yield of 1,2,2,4,6,6-hexamethyl peridinyl-4-acryamide was 2.17 g (84%).

EXAMPLE 12 Synthesis of 1,2,2,6,6-pentamethyl piperidine-4-styrylacetate

1,2,2,6,6-tetramethyl-4-piperidinol (2.5 g, 0.0145 M) was taken in a two necked 50 mL capacity round bottom flask (RB) along with 4-dimethyl aminopyridine (DMAP) (88.5 mg, 0.543 mM) and was kept under nitrogen atomsphere. Dry dichloromethane (30 mL) was injected into the tightly closed RB through the rubber septum, followed by dry triethyl amine (TEA) (2.2 g, 0.0275 M). This reaction mixture was stirred for 20 minutes at room temperature followed by the gradual addition of 3-butenoyl chloride-3-phenyl (styrylacetyl chloride) (0.86 mL, 0.01087 M) with stirring at 0-5° C. initially for 2 hrs. The reaction mixture was then agitated at room temperature for 9 hrs. This reaction mixture was then quenched in ice water, and the product was extracted in dichloromethane (4×25 mL). The combined extract was given (2×20 mL) washes potassium bicarbonate solution and finally dried over anhydrous magnesium sulfate. The solvent was evaporated at 38° C. under vacuum over rotavapor. The product was found to be almost pure (97.2% pure by GC). 1,2,2,6,-pentamethyl piperidine-4-styrylacetate yielded at the end of the reaction was 3.85 g (81.5%). 

What is claimed is:
 1. A vinylic hindered light stabilizer of the formula (I):

wherein R₁ is a (C₁ to C₈) alkyl, hydroxyalky, or cycloalkyl; R₂ is hydrogen or methyl; R₃ is vinyl; R₅ is H or C₁-C₄ alkyl and X is O, NH or (C₁-C₈) alkylamino, provided that said compound is not 4-acrylamido-1,2,2,6,6-pentamethylpiperidine 4-methyl acrylamido-1,2,2,6,6-pentamentylpiperidine, 1-n,butyl-2,2,6,6-tetramethyl-4-acryloyloxypiperidine, 4(N-n-propyl)acrylamido-1,2,2,6,6 pentamethylpiperidine or 4(N-n-butyl)acrylamido-1,2,2,6,6 pentamethylpiperidine. 